Method of testing FPC bonding yield and FPC having testing pads thereon

ABSTRACT

A flexible printed circuit (FPC) having testing pads thereon is provided. The FPC comprises a plurality of bonding pads and a plurality of testing pads, wherein each of the testing pads is disposed corresponding to each of the bonding pads, and the testing pads are electrically isolated from the bonding pads. After the bonding pads of the FPC are bonded to pins of a display, the testing pads are electrically connected to the bonding pads on the FPC via the pins of the display. Therefore, the FPC bonding yield can be determined by measuring the electrical property of the testing pads.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of, and claims the prioritybenefit of, U.S. application Ser. No. 10/637,934 filed on Aug. 8, 2003now U.S. Pat. No. 7,060,513.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a method for testing the flexibleprinted circuit(FPC) bonding yield and an FPC structure, and moreparticularly, to a method for testing the bonding yield between an FPCand a display, and an FPC having testing pads thereon.

2. Description of Related Art

The panel display is generally connected to an external system after themanufacturing process is completed, so as to supply an electric powerand drive the panel display. The method commonly used for connecting thepanel display to the external system presses the FPC onto an edgeportion of the panel display, so that the circuit of the panel displayis electrically connected to the circuit of the FPC. Since the other endof the FPC is connected to an external system, the panel display isconnected to the external system via the connection provided by the FPC.However, since the FPC is weak and can be damaged by external forces,the reliability for the bonding between the FPC and the panel display israther weak. Therefore, a bonding yield test should inevitably beperformed after the FPC is bonded to the panel display.

The method for testing the bonding yield between the FPC and the paneldisplay used in the prior art employs an optical microscope to check thebonding status of the FPC, or tests a bonding strength of the FPC byperforming a pull force testing after the FPC is bonded. However, theconventional measuring method cannot measure the electrical property ofthe bonding for determining whether the panel display can work properlyor not.

In the conventional method for measuring the electrical property of thebonding for determining whether the panel display can work properly ornot, a light on process is commonly performed after the FPC is bonded tothe panel display, so that it is ensured that the FPC is successfullybonded to the panel display. However, there is a problem existing in themethod mentioned above for ensuring that the FPC is successfully bondedto the panel display, that is in the case where an abnormal imageappears on the panel display and it is not sure whether it is caused bya bonding defect occurring between the FPC and the display or caused bya malfunction of a component inside the panel display. It is verycomplicated and hard to find the root cause of the abnormal image.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method for testingthe FPC bonding yield and an FPC having the testing pads thereon, so asto solve the problem that occurred in the prior art in which themeasuring of the electrical property for determining whether the paneldisplay can work properly or not could not be performed.

It is a further object of the present invention to provide a method fortesting the FPC bonding yield and an FPC having the testing padsthereon, so as to solve the problem that occurred in the conventionalmeasuring method, where whether the problem was caused by a bondingdefect occurring between the FPC and the display or caused by themalfunction of the component inside the panel display when an abnormalimage appears on the panel display was not sure.

The present invention provides a method for testing the FPC bondingyield. The method first provides an FPC, wherein the FPC comprises aplurality of bonding pads. Then, a plurality of testing pads is disposedon the FPC, wherein each of the testing pads is disposed correspondingto each of the bonding pads, and the testing pads are electricallyisolated from the bonding pads. In the present invention, the method fordisposing the testing pads on the FPC is forming a plurality ofconductive pads on the FPC, wherein the conductive pads are made of amaterial, such as copper. Furthermore, a plurality of openings is formedon the FPC, and the openings expose the pins of the apparatus that areto be bonded after the subsequent FPC bonding process is completed.Meanwhile, an apparatus to be bonded such as a liquid crystal display isprovided, and the apparatus comprises a plurality of pins thereon. Then,a bonding process is performed, so that the bonding pads and the testingpads of the FPC are electrically connected to the pins of the apparatus.A testing signal is then input to the FPC, and an output signal ismeasured from the testing pads, so as to determine the bonding yieldbetween the FPC and the apparatus. If the output signal measured fromthe testing pads indicates it is abnormal, it means the bonding betweenthe FPC and the apparatus is poor.

The present invention provides a method for testing the FPC bondingyield. The method first provides an FPC, wherein the FPC comprises aplurality of bonding pads. An apparatus to be bonded such as a liquidcrystal display is provided, and the apparatus comprises a plurality ofpins thereon. Then, a boding process is performed, so that the bondingpads of the FPC are electrically connected to the pins of the apparatus,wherein the flexible printed circuit expose a portion of the pins of theapparatus. A testing signal is then input to the FPC, and an outputsignal is measured from the exposed pins, so as to determine the bondingyield between the FPC and the apparatus. If the output signal measuredfrom the exposed pins indicates it is abnormal, it means the bondingbetween the FPC and the apparatus is poor.

The present invention provides an FPC having the testing pads. The FPCcomprises a plurality of bonding pads and a plurality of testing pads,wherein each of the testing pads is disposed corresponding to each ofthe bonding pads, and each of the testing pads is electrically isolatedfrom each of the bonding pads. In the present invention, the testingpads on the FPC are such as a plurality of conductive pads, wherein theconductive pads are made of a material, such as copper. Furthermore, thetesting pads mentioned above may be a plurality of openings.

The present invention provides a method for forming an FPC havingtesting pads. An FPC having a plurality of bonding pads thereon isprovided. A plurality of testing pads is formed on the FPC, wherein eachof the testing pads is formed corresponding to each of the bonding pads,and each of the testing pads is electrically isolated from the bondingpads. In the present invention, the testing pads on the FPC are such asa plurality of conductive pads, wherein the conductive pads are made ofa material, such as copper. Furthermore, the testing pads mentionedabove may be a plurality of openings.

The testing method provided by the present invention immediately knowsthe bonding effect of the FPC, so as to improve the product yield andshorten the product manufacturing process.

Further, since the present invention can immediately know whether theFPC bonding is successful or not, and when it is found that the FPCbonding has failed, the FPC bonding process is immediately reperformed,so as to enhance the product yield.

Furthermore, since the measuring method of the present invention clearlyindicates whether the abnormal image is caused by the poor bonding ofthe FPC or not, the present invention can shorten the time for findingthe root cause of the abnormal condition when the product malfunctions.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention, and together with the description, serve to explain theprinciples of the invention.

FIG. 1 schematically shows a top view of a FPC of a preferred embodimentaccording to the present invention.

FIG. 2 is a diagram for testing the FPC bonding yield of a preferredembodiment according to the present invention.

FIG. 3 is a diagram for testing the FPC bonding yield of anotherpreferred embodiment according to the present invention.

FIG. 4 is a diagram for testing the FPC bonding yield of anotherpreferred embodiment according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 schematically shows a top view of an FPC of a preferredembodiment according to the present invention, and FIG. 2 is a diagramfor testing the FPC bonding yield of a preferred embodiment according tothe present invention.

Referring to both FIG. 1 and FIG. 2, the method for testing the FPCbonding yield provided by the present invention first provides an FPC100, wherein the FPC 100 comprises a plurality of bonding pads 102.Then, a plurality of testing pads 104 is disposed on the FPC 100,wherein each of the testing pads 104 is disposed corresponding to eachof the bonding pads 102, and the testing pads 104 are electricallyisolated from the bonding pads 102.

In a preferred embodiment, the method for disposing the testing pads 104on the FPC 100 is such as forming a plurality of conductive pads 104 onthe FPC 100, and its sectional view (the A-A′ sectional view) is asshown in FIG. 2. The conductive pads 104 are made of a material such ascopper.

Referring to FIG. 2, meanwhile, an apparatus 200 such as a display isprovided, wherein the display 200 comprises a plurality of pins 202.Then, a bonding process is performed, so that the bonding pads 102 andthe testing pads 104 of the FPC 100 are electrically connected to thepins 202 of the display 200. In a preferred embodiment, the bondingprocess is such as disposing a layer of the anisotropic conductiveadhesive 210 in between the FPC 100 and the display 200, then a pressingstep is performed, so that the conductive particles inside theanisotropic conductive adhesive are contacted with each other, and thebonding pads 102 and the testing pads 104 of the FPC 100 are furtherelectrically connected to the pins 202 of the display 200.

A testing signal is then input to the FPC 100, and the testing signal issent to the pins 202 of the display 200 via the bonding pads 102 and theanisotropic conductive adhesive 210, and further sent to the testingpads 104 via the pins 202 and the anisotropic conductive adhesive 210.Therefore, if the FPC bonding is good, a normal output signal ismeasured from the testing pads 104. In other words, the presentinvention determines the bonding yield between the FPC 100 and thedisplay 200 by inputting a testing signal into the FPC 100, andmeasuring an output signal from the testing pads 104. If the outputsignal measured from the testing pads 104 is abnormal, it means thebonding between the FPC 100 and the display 200 is poor.

Furthermore, the method for testing the FPC bonding yield provided bythe present invention forms a plurality of openings 104 a on the FPC100, and the openings 104 a are used as the testing pads as shown inFIG. 3. After the FPC 100 is bonded to the display 200 with the help ofthe anisotropic conductive adhesive 210, the bonding pads 102 of the FPC100 are electrically connected to the pins 202 of the display 200, andthe openings 104 a on the FPC 100 expose the anisotropic conductiveadhesive 210 corresponding to the pins 202.

Then, a testing signal is input into the FPC 100, and the testing signalis then sent to the pins 202 of the display 200 via the bonding pads 102and the anisotropic conductive adhesive 210. If the FPC bonding is good,a normal output signal can be measured from the anisotropic conductiveadhesive 210, which is exposed and correspond to the pins 202, via theopenings 104 a. In other words, the present invention determines thebonding yield between the FPC 100 and the display 200 by inputting atesting signal into the FPC 100, and measuring an output signal from theanisotropic conductive adhesive 210, which is exposed by the openings104 a and correspond to the pins 202. If the measured output signal isabnormal, it means the bonding between the FPC 100 and the display 200is poor.

The FPC 100 having the testing pads 104 provided by the presentinvention comprises a plurality of bonding pads 102 and a plurality oftesting pads 104, wherein each of the testing pads 104 is electricallyisolated to each of the bonding pads 102. In the present invention, thetesting pads 104 on the FPC 100 are such as a plurality of conductivepads (as shown in FIG. 2) thereon, and the conductive pads are made of amaterial, such as copper. Further, the testing pads 104 also can be aplurality of openings (as shown in FIG. 3), and the openings 104 aexpose the pins of the display after the subsequent bonding process iscompleted.

A method for forming the FPC 100 having the testing pads 104 is alsoprovided. Firstly, an FPC 100 having a plurality of bonding pads 102thereon is provided. Then, a plurality of testing pads 104 are formed onthe FPC 100, wherein each of the testing pads 104 is formedcorresponding to each of the bonding pads 102, and each of the testingpads 104 is electrically isolated from the bonding pads 102. In thepresent invention, the testing pads 104 on the FPC 100 can be aplurality of conductive pads (as shown in FIG. 2), wherein theconductive pads are made of a material, such as copper. Furthermore, thetesting pads 104 mentioned above may be a plurality of openings 104 a(as shown in FIG. 3), and the openings 104 a expose the pins of thedisplay after the subsequent bonding process is completed.

In another embodiment of the invention, as shown in FIG. 4, a method fortesting the FPC bonding yield first provides an FPC 100 having aplurality of bonding pads 102 thereon. An apparatus 200 to be bondedsuch as a display is provided, and the apparatus 200 comprises aplurality of pins 202 thereon. Then, a boding process is performed, sothat the bonding pads 102 of the FPC 100 are electrically connected tothe pins 202 of the apparatus 200, wherein the flexible printed circuit100 expose a portion of the pins 202 (as region 400). In a preferredembodiment, the bonding process is such as disposing a layer of theanisotropic conductive adhesive 210 in between the FPC 100 and thedisplay 200, then a pressing step is performed, so that the conductiveparticles inside the anisotropic conductive adhesive are contacted witheach other, and the bonding pads 102 are electrically connected to thepins 202 of the display 200.

Then, a testing signal is input into the FPC 100, and the testing signalis then sent to the pins 202 of the display 200 via the bonding pads 102and the anisotropic conductive adhesive 210. If the FPC bonding is good,a normal output signal can be measured from the anisotropic conductiveadhesive 210, which is the region 400 exposed by the FPC 100. In otherwords, the present invention determines the bonding yield between theFPC 100 and the display 200 by inputting a testing signal into the FPC100, and measuring an output signal from the anisotropic conductiveadhesive 210, which is the region 400 exposed by the FPC 100. If themeasured output signal is abnormal, it means the bonding between the FPC100 and the display 200 is poor.

The method for testing FPC bonding yield provided by the presentinvention immediately knows the bonding effect of the FPC, so as toimprove the product yield and shorten the product manufacturing process.

Further, the present invention can immediately know whether the FPCbonding is successful or not, and when it is found that the FPC bondinghas failed, the FPC bonding process is immediately reperformed, so as toenhance the product yield.

Furthermore, since the measuring method of the present invention clearlyindicates whether the abnormal image is caused by the poor bonding ofthe FPC or not, the present invention can shorten the time for findingthe root cause of the abnormal condition when the product malfunctions.

Although the invention has been described with reference to a particularembodiment thereof, it will be apparent to one of the ordinary skill inthe art that modifications to the described embodiment may be madewithout departing from the spirit of the invention. Accordingly, thescope of the invention will be defined by the attached claims not by theabove detailed description.

1. A bonding structure between a flexible printed circuit and anapparatus, comprising: a plurality of bonding pads provided on theflexible printed circuit; a plurality of testing pads provided on theflexible printed circuit, wherein each of the testing pads is disposedcorresponding to each of the bonding pads, and the testing pads areelectrically isolated from the bonding pads; and a plurality of contactpins provided on the apparatus, wherein each bonding pad and thecorresponding testing pad of the flexible printed circuit are bothconductively bonded to same corresponding contact pin of the apparatusto form an electrical conductive path from each bonding pad to thecorresponding testing pad of the flexible printed circuit via thecorresponding contact pin of the apparatus, whereby integrity ofconductive bonding between the flexible printed circuit and the contactpins can be determined by testing the electrical conductive path.
 2. Thebonding structure as in claim 1, wherein the apparatus is a display. 3.The bonding structure as in claim 1, wherein the testing pads on theflexible printed circuit are conductive pads.
 4. The bonding structureas in claim 1, wherein the testing pads on the flexible printed circuitare provided in openings.
 5. The bonding structure as in claim 4,wherein the flexible printed circuit is conductively bonded to theapparatus to define a bonding area, and the openings for the testingpads are provided on the flexible printed circuit within the bondingarea, wherein integrity of conductive bonding between the flexibleprinted circuit and the contact pins can be determined by testing theelectrical conductive path with the bonding area.
 6. The bondingstructure as in claim 1, wherein the bonding pads are exposed at a firstplanar surface of the flexible printed circuit which faces the contactpins of the apparatus, and the testing pads are exposed at the firstplanar surface and an opposite second planar surface of the flexibleprinted circuit.
 7. The bonding structure as in claim 1, furthercomprising a conductive bonding material conductively bonding thetesting pads and bonding pads of the flexible printed circuit and thecontact pins of the apparatus.
 8. The bonding structure as in claim 7,wherein the bonding material comprises a conductive adhesive.
 9. Thebonding structure as in claim 8, wherein the conductive adhesive is ananisotropic conductive adhesive.
 10. The bonding structure as in claim1, wherein the flexible printed circuit is conductively bonded to theapparatus to define a bonding area, and the testing pads are providedwithin the bonding area, wherein integrity of conductive bonding betweenthe flexible printed circuit and the contact pins can be determined bytesting the electrical conductive path within the bonding area.
 11. Thebonding structure as in claim 10, wherein the bonding area is defined ata terminal end of the flexible circuit board, which connects to the pinsof the apparatus.
 12. A bonding structure of a flexible printed circuitfor conductive bonding to a plurality of contact pins of an apparatus,comprising: a plurality of bonding pads supported on the flexibleprinted circuit, wherein the bonding pads are exposed at a first planarsurface of the flexible printed circuit; and a plurality of testing padssupported on the flexible printed circuit, wherein each of the testingpads is disposed corresponding to each of the bonding pads, wherein thetesting pads are electrically isolated from the bonding pads, andwherein a first surface of each testing pad is exposed at the firstplanar surface, and an opposite second surface of each testing pad isexposed at an opposite second planar surface of the flexible printedcircuit to allow testing when the first surface of the testing pads andthe bonding pad are bonded to the contact pins of the apparatus; whereineach bonding pad and the corresponding testing pad of the flexibleprinted circuit are both conductively bonded to same correspondingcontact pin of the apparatus to form an electrical conductive path fromeach bonding pad to the corresponding testing pad of the flexibleprinted circuit via the corresponding contact pin of the apparatus,whereby integrity of conductive bonding between the flexible printedcircuit and the contact pins can be determined by testing the electricalconductive path within the bonded area.
 13. The bonding structure as inclaim 12, wherein each testing pad is provided in a through opening inthe flexible printed circuit, exposing the second surface of testing padto allow access to the second surface of each testing pad at the secondplanar surface of the flexible printed circuit.
 14. The bondingstructure as in claim 12, wherein a bonding area is defined in theflexible printed circuit where the flexible printed circuit is bonded tothe contact pins of apparatus, and wherein the testing pads are providedwithin the bonding area.
 15. A bonding structure of a flexible printedcircuit for conductive bonding to a contact pin of an apparatus,comprising: a first conductive pad exposed on a first planar surfacewithin a bonding area of the flexible printed circuit; a secondconductive pad exposed on the first planar surface within the bondingarea of the flexible printed circuit, wherein the second conductive padis electrically isolated from the first conductive pad, and wherein thefirst conductive pad and the second conductive pad of the flexibleprinted circuit are both conductively bonded to same contact pin of theapparatus to form an electrical conductive path from the firstconductive pad to the second conductive pad of the flexible printedcircuit via the corresponding contact pin of the apparatus, wherebyintegrity of conductive bonding between the flexible printed circuit andthe contact pin can be determined by testing the electrical conductivepath between the first conductive pad and the second conductive padwithin the bonding area.
 16. The bonding structure as in claim 15,wherein the bonding area is defined at a terminal end of the flexibleprinted circuit.
 17. The bonding structure as in claim 16, wherein thefirst conductive pad is a bonding pad of the flexible printed circuit,and the second conductive pad is a testing pad of the flexible printedcircuit.